Viscometer



Dec. 15, 1959 c. J. H. MONK 2,917,065

VISCOMETER Filed Aug. 13, 195'? INVENTOR CrR/L JAMES ///V/?YMOWK CLAW/WWW ATTORNEYS VISCOMETER Cyril James Henry Monk, Burnham, England, assignor to Imperial Chemical Industries Limited, London, England, a corporation of Great Britain Application August 13, 1957, Serial No. 677,984 Claims priority, application Great Britain August 13, 1956 1 Claim. (Cl. 137-92) This invention relates to an automatic device for controlling the viscosity of a liquid by mixing with it a second liquid. In particular, the invention provides an apparatus for reducing the viscosity of a liquid to a predetermined value by the automatic addition of a second liquid, a thinner, in an appropriate quantity.

In the oil, paint and other industries it is frequently necessary to prepare a sample or bulk quantity of a liquid at a certain predetermined viscosity. Hitherto this has largely been done by trial and error using a standard viscosity cup or some other form of viscometer to measure the viscosity of the sample as thinning proceeds.

This invention provides an apparatus in which a sample can be thinned automatically to a predetermined viscosity. This invention provides an apparatus which comprlses in combination a torsional viscometer and flow control means for thinner additions, and an operative connection between a moveable member of the viscometer and the flow control means whereby the flow of thinner will be controlled in accordance with the viscosity attained 1n the viscometer.

In one form the apparatus comprises in combmation a torsional viscometer and an air control system, including an air vane and an air jet for controlling the addition of the thinner to liquid in the viscometer contamer, the air vane of the control system being moveable by part of the viscometer to which torsion is transmitted.

In a preferred form of the invention the flow control means for thinner addition comprises an air jet and an air vane for closing the air jet either the vane or the jet being moveable by part of viscometer to which torsion is transmitted, and an air line which feeds the jet and communicates with a closed thinner reservoir, which in turn communicates with the viscometer container. The relative position of the air vane and air jet are preferably relatively adjustable.

In one form of the invention the quantity of the second liquid added to a known quantity of liquid to produce the desired viscosity in measured and hence the thinning ratio calculated.

The stirrer of the viscometer may be rotated by any suitable motor and it is preferred to use an air motor since fire hazards are eliminated. The speed of rotation of the motor should be such that largely laminar flow exists in the viscometer. Under these circumstances the torque transmitted is closely related to the viscosity of the medium and independant of its density. Furthermore, if there is a certain amount of turbulence the liquids are more easily mixed. Speeds of the order of 500 r.p.m. have been found to be satisfactory. The relative sizes of the stirrer and container may be varied so enabling the apparatus to handle samples of widely varying viscosity. Furthermore, the position of the tension device attached to the spindle of the viscometer stand may be varied so providing yet another means of alteringthe viscosity range covered by the apparatus.

The stirrer for use in this invention may be in the form of a disc mounted at the end of a shaft and the disc is preferably provided with a number of holes designed to increase the mixing efliciency of the stirrer, without unduly affecting the flow conditions mentioned earlier.

It must be noted that in the event of the container being made separate from the viscometer stand it is essential for the container to be firmly attached to the stand, since if slipping occurs inaccurate results may be obtained. When a separate ferromagnetic container is used, such as a tin, slipping can be prevented by fitting magnets onto the viscometer stand.

The design of the air control system which controls the addition of the second liquid requires some care. It has been found that using either the air actuated liquid control valve system or the direct feed back of air pressure to the closed thinner reservoir the apparatus works most satisfactorily when the jet at the end of the air line is large in comparison with the flow of air to the jet. This condition can be fulfilled by the insertion in the air line leading to the jet of a constriction of small diameter in comparison with that of the jet.

Two forms' of the apparatus will now be described by reference to the accompanying diagrams:

Fig. I is a vertical section through an automatic thinner employing an air valve.

Fig. II is a vertical section showing container etc. for an automatic thinner employing back pressure thinner feed.

Fig. III is a view on the line AA (Fig. I) of the base unit of the apparatus, which is common to Fig. I and Fig. II.

Now referring to Fig. I a standard size container 1 stands on a rotatable stand 2. The stand is rigidly fixed to a rotatable spindle 3 which is supported by two bearings 4 mounted on a case 5. One end of a spring 6 is attached to the spindle by an adjustable collar 7 and its other end is fixed to the case 5. A lever 8 is mounted on the spindle 3 by a movable collar 9. The lever 8 incorporates a vane 10 which when the stand is rotated comes into contact with an air jet 11 and closes this jet. The position of the lever 8 is measured on a scale 20 which will, after calibration of the apparatus, indicate the viscosity of the thinned liquid, in the container 1.

A standard size cylindrical stirrer 14 is rotated by an air motor 13 supplied by a pipe 12 with compressed air. A reducing valve 15 and a constriction 116 reduce sub stantially the air pressure in the pipes leading to an air valve 17 and the jet 11. The flow of thinner from a tank 19 into the container 1 through a jet 18 is controlled by the air valve 17. The valve 17 is operated by low air pressure built up in the air lines as a result of the jet 11 being closed by the vane 10.

In Fig. II is shown the modified control means governing the supply of thinner to the viscometer container shown as 1 in Fig. I.

In Fig. II as in Fig. I the air supply is connected to pipe 12 which supplies air to a motor 13 and, via the constriction 16, to the jet 11. A thinner reservoir 22 is connected to the air line 12 and by a pipe 23 to the jet 18. Obviously the position of the reservoir 22 relative to the jet 18 must be such that the thinner only flows from the jet when pressure develops in the reservoir due to the closing of the jet 11 by the vane 8.

This apparatus must be calibrated before use by using liquids of known viscosities of the same order as the desired viscosity to which samples are to be thinned. The calibration must be repeated if the spring 6 is altered relative to the spindle 3, also if a stirrer of different dimensions is used. For any setting of the spring and for a particular stirrer a range of viscosities may be covered by measuring the position of the lever 8 on the scale Patented Dec. 15, 1959 20. Once an appropriate calibration has been made the sequence of operations involved in the use of my apparatus is broadly as follows.

The airline 12 is connected to a supply of compressed air at about 30 lbs./ sq. in. pressure and the reducing valve 15 is set to produce a pressure of about lbs./ sq. in. at the constriction 16. Reservoir 22 and the pipeline con necting it to the jet 18 are filled with, for example, white spirit. A sample of, for example, an oleoresinous varnish is added to the container 1 and the motor and stirrer (.13 and 14) are lowered until the stirrer is completely covered by the varnish. Air is passed into the motor 13 causing it to rotate the stirrer 14. With the apparatus shown in the diagrams the direction of rotation of the stirrer would be clockwise. If the viscosity of the sample to be thinned is greater than the predetermined viscosity torque transmitted from the stirrer 14 by the liquid and the container 1 to the table 2 and so to the spindle 3 will be operated against the spring 6 and the table 2 and the lever 8 will be turned in a clockwise direction causing the vane 10 to close the jet 11. The closing of the jet causes an increase in pressure in the air line which acts on the upper surface of the white spirit in the reservoir 22 and causes it to flow from the reservoir 22 into the container 1. It is desirable that the white spirit should be added to the container close to the stirrer 14. This causes a reduction in the viscosity of the varnish surrounding the stirrer 14 so reducing the torque transmitted permitting the spring 6 to rotate the spindle 3 and Vane 10 away from the jet 11, so opening this air jet. This action stops the flow of white spirit through the jet 18 by reducing the pressure on the surface of the white spirit in the reservoir 22. As the white spirit mixes with the varnish the viscosity will rise, so causing a further addition of thinner by the same process. This procedure is automatically repeated until the viscosity reaches that required.

It is possible, if the size of the original sample is known and the quantity of white spirit added has been measured, to calculate the quantity of thinner required to thin a large known quantity of varnish.

It is obvious from the foregoing description that by suitable modifications to the direction of rotation of the viscometer table and to the air control system the apparatus can be used to raise the viscosity of a suitable sample. Such modifications are within the scope of my invention.

What I claim is:

Apparatus for controlling the viscosity of a liquid, comprising, a torsional viscometer including means for confining a liquid, means for effecting rotational movement of said liquid, said confining means including a member movable in response to torsional forces transmitted thereto by said rotating liquid, a vane mounted for movement along a predetermined path, spring means resiliently urging said vane in one direction along. said path, and means connected between said member and said vane for moving the latter into different positions along said path against the action of said spring means in accordance with the torsional force transmitted to said member by said rotating liquid, conduit means for directing a supply of a second liquid into said confining means, a pressurized air system including an air jet positioned to discharge in the path of movement of said vane whereby the air pressure in said system will vary in accordance with the position of said vane in its path of movement with respect to said air jet, and means operable in response to changes in the air pressure of said system for controlling the flow of said second liquid into said confining means through said conduit means.

References Cited in the file of this patent UNITED STATES PATENTS 2,171,312 Meyers Aug. 29, 1939 2,773,507 Norris Dec. 11, 1956 FOREIGN PATENTS 810,269 France Dec. 28, 1936 

